The present invention relates to the field of testing systems. In particular, embodiments of the invention include exemplary systems adapted to test sealed structures containing one or more gasses as well as having one or more seals adapted to retain such gasses within the sealed structure(s).
A variety of sealed structures exist which have aspects of their apparatus, assembly, assemblies and/or parts sealed at one or more points in a manufacturing process or within a distribution or utilization chain which require subsequent testing. In some cases sealing provides a particular desired effect such as an increase in shelf life or safety related effects. Sealing can be done in combination with other manufacturing or testing steps such as insertion of one or more gasses within the sealed structure which can provide one or more desired effects. Leak testing or seal integrity testing is desirable to ensure desired effects are provided and predictable throughout a desired life cycle including shelf life, transportation, and use.
For example, military safety arming devices (SAD) can be hermetically sealed during initial manufacture. After the safety arming devices are sealed relative to a structure or combination of structures, then such a device and/or structure can be tested to ensure relevant structure(s) and/or seal(s) are functioning as intended and therefore no leakage has occurred. Buyers of such sealed products or structures can perform testing such as lot acceptance testing (LAT) to determine if such seals are in fact performing as desired. All or parts of such device(s), structure(s), assemblies, etc, e.g., SAD, can be tested as a part of LAT. After acceptance or sale, periodic testing can be done on such device(s), structures, assemblies, etc, e.g., SAD, to be evaluated at periodic intervals through surveillance testing which also check assets having, for example, sealed structures such as, e.g., SADs, after exposure to in-service use, shelf conditions, etc to determine if a seal or sealed assembly is still properly sealed. A fine leak test can be performed by a mass spectrometer to determine if any device, assembly, part, structure, etc has experienced a seal failure or loss of integrity that would allow, e.g., interior structure environments to be impacted by such a loss of seal or integrity.
In this example, a SAD can be designed so that in a standard atmosphere the SAD shall not leak helium at a rate greater than 5×104 standard atmosphere cubic centimeters per second (std atm em 3/S). In addition a vacuum immersion test (VIT) (sometimes called a gross leak test) can be performed to look for where a hermetical seal may be broken. Frequently a failure can occur around either the SAD window or another structure, such as a launch latch window. However leaks can also occur at an electrical connector or along the case. A VIT can be performed by placing the SAD in a Vacuum Immersion Bell Jar (VEBJ) filled with isopropyl alcohol (instead of water) and looking for leakage from the SAD. A test requirement can include a need that the SAD shall not leak gas as evidenced in alcohol or de-ionized water by a continuous stream of bubbles emanating from the SAD. Other devices that are hermetically sealed can be tested using this equipment.
One method of testing a SAD can require manual lifting of a heavy part of either or both a test apparatus, test apparatus section, and/or SAD component that creates significant stress/strain to a test operator and required substantial time and effort to perform necessary SAD testing. Such an approach could not only be very labor intensive but suffered from disadvantages such as how sometimes a testing device failed to lock properly in a test set which creates a safety concern. Various disadvantages to such a test approach include damage to a SAD device, test apparatus or injury to a test operator e.g., smash a finger of the operator. Other disadvantages to current methods or systems exist as well such as a substantial probability of bursting a test enclosure e.g., VEBJ. A test operator was required to act quickly and perform several operations and involve in different areas to start a test thus frequently an operator experienced difficulty in focusing on different operations quickly which created substantial opportunity for error. As a result, such testing was requiring excessive duration for testing. An embodiment of the invention provides a variety of advantages to mitigate problems such as discussed above as well as providing reduced testing time (less than half).
According to an illustrative embodiment of the present disclosure, a testing system can include a vacuum test chamber apparatus including a transparent container, e.g., cylindrical structure, capable of withstanding a predetermined pressure differential, e.g., approximately one atmosphere of a pressure differential, and a removable vacuum-tight cover. An actuator, e.g. pneumatic actuator, is provided which raises or lowers the transparent container. A test fixture or platform adapted to hold or support a device under test is provided. The test fixture or platform is formed to fit moveably within the walls of the test chamber's transparent container as well as having a number of holes formed in the fixture or platform adapted to permit free flow of gas or fluid past the test fixture or platform.
An aspect of an embodiment of the invention enables movement of the transparent container up or down relative to the test fixture or platform which is fixed in position relative to the transparent container. Movement of the transparent container upward encapsulates or surrounds the test fixture or platform by the transparent container walls in an extended/un-retracted position. Retraction or lowering the transparent container lowers or retracts the transparent container while the test fixture or platform remains fixed while a device under test remains fixed. The test fixture or platform is supported by a supporting mechanism which, in this embodiment a rod, passes through an aperture in the transparent container so that the fixture or platform remains fixed relative to movement of the container's walls around the fixture or platform.
An immersion liquid is provided in the transparent container which passes through the test fixture or platform when the transparent container is raised and thereby immerses a device under test when the transparent container is raised or extended. In one embodiment, alcohol is used as an immersion fluid which does not degrade the device under test. The immersion liquid falls relative to the test fixture or platform when the transparent container is lowered and thereby exposes the device under test. A variety of ways can be provided to raise or lower the transparent container relative to the test fixture or platform.
An exemplary embodiment can also include a control panel, a vacuum pump or manifold designed to communicate with a vacuum source, a vacuum gage, a source of motive power to the transparent chamber movement control mechanism, an inlet tube from the source of vacuum coupled to the transparent container in an area of the transparent container not submersed by the immersion liquid as well, in some embodiments, an outlet tube.
An exemplary embodiment of a vacuum test chamber, e.g., transparent chamber, has a sealed aperture in the bottom which permits a cylindrical section a pneumatic actuator to extend and retract in the test chamber so as to prevent either air or liquid in the chamber from exiting the chamber past the sealed aperture. An exemplary device under test or test sample and test fluid can also be held at equilibrium with normal room temperature in some embodiments. Procedures for testing are presented herein as well.
Additional features and advantages of the present invention will become apparent to those skilled in the art upon consideration of the following detailed description of the illustrative embodiment exemplifying the best mode of carrying out the invention as presently perceived.